In the past, devices have employed transmissions for varying the rotational speed of an output shaft relative to the rotational speed of an input shaft. Many of these transmissions include a plurality of gears coupled to the output shaft, any one of which may be engaged with a respective gear on the input shaft to achieve a desired gearing ratio. The number of gearing ratios available with these transmissions is limited by the number of gears provided on the output shaft. In addition, the input and output shafts must be momentarily disengaged in order to select a new gearing ratio. This introduces discontinuities into the acceleration or deceleration of the output shaft.
Continuously variable pulley transmissions have been employed in vehicle power train transmissions. These transmissions require a separate mechanism in order to simultaneously adjust the configuration of the input and output shaft pulleys thereby adding to the size and complexity of the transmission.
Thus, there is need for a less complicated transmission which is capable of providing a wide range of gearing ratios while minimizing any discontinuities in the acceleration and deceleration of the output shaft.